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[ANSYS Meshing] Hot to change the O grid in the following pipe

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Old   May 3, 2013, 02:11
Default Hot to change the O grid in the following pipe
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Dear friends:
I use O grid to generate mesh for a ellipse pipe, i not want to change the rectangular edge in the center of the pipe to a circle so as o further improve the quality of mesh.
but how to change the edge in to a circle?
Regards
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Old   May 3, 2013, 02:42
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I donīt understand what you mean. Do you want to adecuate the edges to your geometry?

You can edit the edge so you get a edge with the same shape.

Blocking -> Edit edge -> Split Edge -> Automatic Linear.

Then select the edge you want and you get the same shape of the curve.

If you want to use "Automatic linear" you have to "update" before.
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Old   May 3, 2013, 03:04
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Do you want the inner block to be a cylinder? If so, don't do it. It degrades the mesh at the points of intersection of the edges. That's why you use an O-grid at all - to blend from the outer circle to an inner rectangle.
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Old   May 3, 2013, 05:56
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Quote:
Originally Posted by RodriguezFatz View Post
Do you want the inner block to be a cylinder? If so, don't do it. It degrades the mesh at the points of intersection of the edges. That's why you use an O-grid at all - to blend from the outer circle to an inner rectangle.
yes, i want the inner block to be a cylinder. but i think if it is a cylinder, then we can use a cylindrical coordinate mesh , it is orthogonal. why you say it degrades the mesh?
thank you
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Old   May 3, 2013, 06:01
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Maybe I don't get you right, but can you draw a simple sketch, how you want the mesh to look like at the face?

good:
good.jpg

bad: (not all lines are drawn)
bad.jpg

bad, too:
bad2.jpg
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Old   May 3, 2013, 08:49
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Quote:
Originally Posted by RodriguezFatz View Post
Maybe I don't get you right, but can you draw a simple sketch, how you want the mesh to look like at the face?

good:
Attachment 21431

bad: (not all lines are drawn)
Attachment 21432

bad, too:
Attachment 21433
Dear friends:
I merge the four vertices of the inner block, then i get this . but the vertice is not at the center position.
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Old   May 3, 2013, 09:10
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But how do the center cells looks like? It is exactly the same bad shape as in my second "bad"-case: distorted triangles. This isn't hexa any longer and also for tri mesh it would be bad!
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Old   May 3, 2013, 16:01
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If you do exactly you said before you get this picture. Iīve moved the vertex to the center of the cylinder and I get this. But...as Phillip said before... you get bad quality elements as you can see in the quality histogram.
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File Type: jpg 2.jpg (49.1 KB, 20 views)
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Old   May 6, 2013, 03:26
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I would like to know how to do this but with mesh mix. I mean, with hexas and in the center of the cylinder with tri elements. Is that possible? I know in ANSYS Meshing is possible but, can I do it in ICEM CFD too?
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Old   May 6, 2013, 03:31
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I think that works, but I wouldn't do that. I don't see any reason why you would try to get tri elements into a pipe. Hexa elements have the better quality anyway. Especially in pipes, where the flow is orthogonal to the faces most of the time. Also (nearly) everyone meshes a pipe like I show in picture no. 1.
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Old   May 6, 2013, 03:59
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Yes, youīre right. I always mesh the pipe in that way. But I ask this, because I need this form to make the mesh. Itīs better to me, to coupling with an turboīs shaft. So, I would like how to do this.
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Old   May 6, 2013, 04:05
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Why don't you just post the complete geometry? That would cause less confusion...
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Old   May 6, 2013, 04:27
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I donīt have the geom. Itīs a case that I want to prove. A friend of mine asked me something similar the other day and I didnīt know how to respond to him. So, for that, Iīve asked it here. And because I would like to do a simple case like this mixing meshes.
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Old   May 6, 2013, 04:34
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Alright! Good luck...
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Old   May 6, 2013, 05:08
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You just merge the 4 vertices of the inside block of O-grid. The you will get what you wanted.
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